definition, origin, and distribution

1. Phosphate RockPhosphate Rock
Supervision by: Dr. Ahmed M. ZayedSupervision by: Dr. Ahmed M. Zayed
Edited by : Mostafa Abdel Azim MasoudEdited by : Mostafa Abdel Azim Masoud
Beni-Suef University- EgyptBeni-Suef University- Egypt

2. IntroductionIntroduction
-Rock Phosphate or Phosphate rock is a-Rock Phosphate or Phosphate rock is a non-detritalnon-detrital sedimentary rock whichsedimentary rock which
contains high amounts of phosphate bearing minerals.contains high amounts of phosphate bearing minerals.
-The phosphate content of phosphorite is at least 15 to 20 %.-The phosphate content of phosphorite is at least 15 to 20 %.
-The phosphate is present as fluorapatite Ca5(PO4)3F (CFA) typically in-The phosphate is present as fluorapatite Ca5(PO4)3F (CFA) typically in
cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane.cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane.
-It is also present as hydroxyapatite Ca5(PO4)3OH, which is often dissolved from-It is also present as hydroxyapatite Ca5(PO4)3OH, which is often dissolved from
vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermalvertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal
veins (igneous origin).veins (igneous origin).
-Phosphorite deposits often occur in extensive layers, which cumulatively cover tens-Phosphorite deposits often occur in extensive layers, which cumulatively cover tens
of thousands of square kilometres of the Earth's crust.of thousands of square kilometres of the Earth's crust.
-In sedimentary apatite replacement of the phosphate by carbonate may reach several-In sedimentary apatite replacement of the phosphate by carbonate may reach several
percent and fluorine may be replaced by hydroxyl or chlorine ions. In addition to, thepercent and fluorine may be replaced by hydroxyl or chlorine ions. In addition to, the
calcium ions may be substituted bycalcium ions may be substituted by Na, Sr, U, and Rare EarthsNa, Sr, U, and Rare Earths..

3. MineralogyMineralogy
Very important note:
Apatite is the principal primary mineral, but a number of others are common in
deposits formed during weathering of phosphate rock and guano.
Examples are brushite (HCaP04 2H20), monetite (HCaP04), whitlockite (/3-
Ca3 (P04 ) 2 ), crandallite (CaAL- (P04 ) 2 (OH) 5-H20), wavellite (A13 (OH)
3 (P04 )2-5H20), taranakite (K2A16 (P04 ) 6 (OH) 2-18H20), millisite
(Na,K)CaAl6 (P04 ) 4 (OH) s- 3H20), variscite (A1P04-2H20), and strengite
(FeP04-2H20)..
Phosphate rock Phosphorite Guano
rocks of any origin that
contain more than about 20
percent P2O5.
phosphate rocks of marine
origin.
accumulations of animal
excrement, altered to
various degrees through
hydration, oxidation,
and leaching.

4. Depositional environmentsDepositional environments
Phosphates are deposited in a wide range of depositional environments.Phosphates are deposited in a wide range of depositional environments.
Normally phosphates are deposited inNormally phosphates are deposited in very shallow, near shore marine or lowvery shallow, near shore marine or low
energy environmentsenergy environments. This includes environments such as. This includes environments such as supratidal zones,supratidal zones,
littoral or intertidal zones, and most importantly estuarinelittoral or intertidal zones, and most importantly estuarine..
Supratidal zones:Supratidal zones: the supratidal zone lies in the supratidal zone lies in a very high tide levela very high tide level ..
Littoral environments/ intertidal zones:Littoral environments/ intertidal zones: The intertidal zone is located The intertidal zone is located withinwithin thethe
mean high and low tide levelsmean high and low tide levels ..The zone contains both suspension sedimentationThe zone contains both suspension sedimentation
and bed load.and bed load.
Estuarine environmentsEstuarine environments : Estuarine environments, are located at the lower parts of: Estuarine environments, are located at the lower parts of
rivers that streamrivers that stream into the open sea. Estuaries are also known as a phosphorus “trap”.into the open sea. Estuaries are also known as a phosphorus “trap”.
The most common occurrence of phosphorites are related toThe most common occurrence of phosphorites are related to strong marinestrong marine
upwellingupwelling of sedimentsof sediments. Upwelling is caused by. Upwelling is caused by deep water currentsdeep water currents . This type of. This type of
environment is the main reason why phosphorites are commonly associated withenvironment is the main reason why phosphorites are commonly associated with silicasilica
and chertand chert ..

5. Model for formation of marine phosphoritesModel for formation of marine phosphorites

6. Types of phosphorite depositionTypes of phosphorite deposition
Phosphate nodules:Phosphate nodules:
These are spherical concentrations. Most phosphorite grains are sand size. TheseThese are spherical concentrations. Most phosphorite grains are sand size. These
larger grains, referred to as larger grains, referred to as nodulesnodules, can range up to several tens of centimeters in, can range up to several tens of centimeters in
size. The internal structure of nodules various from homogeneous to concentrically-size. The internal structure of nodules various from homogeneous to concentrically-
laminated and conglomeratic and many containlaminated and conglomeratic and many contain pellets and ooidspellets and ooids andand vertebratevertebrate
skeletal debris of fishskeletal debris of fish may be present. The principal mineral ismay be present. The principal mineral is collophanecollophane, but, but
francolitefrancolite andand dahlitedahlite are also present.are also present. GlauconiteGlauconite may be present.may be present.
Bioclastic phosphates or bone bedsBioclastic phosphates or bone beds ::
Bone beds are bedded phosphate deposits that contain concentrations ofBone beds are bedded phosphate deposits that contain concentrations of
vertebrate skeletal particles such fish. Some also contain invertebrate fossils likevertebrate skeletal particles such fish. Some also contain invertebrate fossils like
brachiopods and become more enriched inbrachiopods and become more enriched in P205 after digenetic processes have after digenetic processes have
occurred. Bioclastic phosphates can also be cemented by phosphate mineralsoccurred. Bioclastic phosphates can also be cemented by phosphate minerals..
Phosphatization (Guano)Phosphatization (Guano) ::
Phosphatization is a type ofPhosphatization is a type of rare diagenetic processesrare diagenetic processes . It occurs when fluids. It occurs when fluids
that are rich in phosphate are leached fromthat are rich in phosphate are leached from guanoguano.. These are then concentrated These are then concentrated
and reprecipitated in limestone.and reprecipitated in limestone.

7. Introduction to the origin of phosphateIntroduction to the origin of phosphate
Apatites of igneous origin:
include hydrothermal veins, and pegmatites, but the largest deposits are
intrusive masses or sheets associated with carbonatite, nepheline-syenite,
and other alkalic rocks.
Sedimentary phosphorites
Most of the world's phosphate production comes from marine
phosphorites, many of which are associated with black shale and chert.
Guano deposits:
Consist of natural accumulation of the excrement of bats or, more
importantly, Seafowl , altered to various degrees through dehydration,
oxidation.
Primary deposits Secondary deposits
include igneousapatites,
sedimentary phosphorites, and
guano.
diagenetic phosphatization of
calcium carbonate and
.interstitial precipitation,
reworking by waves and
currents, and weathering

8. APATITE DEPOSITS OF IGNEOUS
ORIGIN
Apatite deposits of igneous origin occur as intrusive masses or sheets,
as hydrothermal veins, along or near the boundaries of intrusions, or as
pegmatite.
The intrusive masses are the largest of these deposits. They are commonly
associated with alkalic igneous rock complexes, many of which such as those
in Africa, Brazil, and Sweden are associated with rift valley structures.
Carbonatite, Nepheline- Syenite, and Pyroxenite are common members of the
rock assemblage.

9. SEDIMENTARY PHOSPHORITE AND WEATHERING
DERIVATIVES
Most of the world's phosphate production comes from marine phosphorites. The
richest and largest of these form in areas of upwelling associated with
divergence, chiefly along the west coasts of the continents or, in large Mediterranean
sea.
The typical lateral sequence of rocks, in a shoreward direction, consists of dark
carbonaceous shale, phosphatic shale, phosphorite, and dolomite; chert or
diatomite.
Thicker and richer deposits may occur locally but are highly lenticular In Israel
(Bentor, 1953) and Egypt (Youssef, 1965) such deposits are localized in synclines that
evidently represented shallow depressions at the time of deposition.
Phosphate deposits that formed in the warm-current environment consist of
phosphatic limestone or sandstone. Chert, black shale, and salines are not
associated with these deposits, and they are less extensive and lower in grade than
the deposits formed from cold currents.
Glauconite, associated with the marine phosphorites in many places, contains from 1 to
5 percent P205, and because it also contains potash it has had some use as a
fertilizer (Mansfield, 1922). Some sedimentary iron ores contain a few percent P205
(Geijer, 1962; Davidson, 1963).

10. GUANO AND RELATED DEPOSITS
Most of the large accumulations of guano are formed at the surface by
seafowl excrements , but smaller quantities are formed by bats and to a
lesser extent by other cave-dwelling mammals and birds (Hutchinson, 1950).
Most of them have been measured in hundreds or thousands of tons. Seafowl
deposits are mainly confined to islands and coastal regions in low
latitudes. The largest lie along the west coasts of Lower California, South
America, and Africa, and on islands near the equatorial currents.
Modern guano contains 10-12 percent P2O5, but leached guano contains
20-32 percent. The mineralogy of guano is complex.
The mineralogy of phosphatized rocks derived from guano depends on the
composition of the host rock. Where it is limestone, the phosphate mineral is
apatite; but where the underlying rock is a silicate, as in islands of volcanic
origin, the phosphate minerals are aluminum or aluminum-iron
phosphates.

11. Phosphate rock (Phosphorites) in EgyptPhosphate rock (Phosphorites) in Egypt
-Case study (Abu Tartur)
Occurs in the scarp face bounding the Dakhla
Kharga depression in the western desert.
-The phosphate bearing formation of the
campanian-Maastrichtian age overlies
unconformably the variegated shale unit of the
Nubia formation and is turn capped
conformably by the Dakhla shales.
The phosphatic matter occurs in the form of
pellets , oolites, nodules and concretions.
The phosphatic minerals include carbonate
apatite (collophane) and francolite- dahlite with
wavellite.
The non phosphatic minerals are represented
by dolomite, ankerite (carbonate),
montmorillonite, calcite, gypsum, iron oxide,
pyrite, glauconite and carbonaceous matter.
Unfortunately, the occasional presence of iron
sulfides affects the workability of these
reserves.